The present invention generally relates to a sputtering apparatus and more particularly, to a sputtering apparatus to be used in a reactive sputtering, which mixes a reactive gas into discharge gas so as to form compound thin membranes.
Generally, a reactive sputtering apparatus is generally used so as to form the compound thin membrane by a reactive sputtering method of mixing the reactive gas into the discharge gas or to optionally vary the composition ratio of the compound by the controlling of the flow amount of the reactive gas.
The above-described reactive sputtering apparatus will be described hereinafter with reference to FIG. 6, which is a sectional view of the conventional sputtering apparatus, including a chamber 24 capable of effecting an exhaust operation therein, a basic plate 25 disposed within the chamber 24 so as to form thin membranes, a basic plate holder 26 for retaining the basic plate 25 so as to turn it on its own axis or to revolve around the sun, a metallic target disposed opposite to the basic plate 26, a backing plate 28 for retaining the target 27, cooling water supply means 29 for cooling the backing plate 28, Ar gas supply means 30, O.sub.2 supply means 31, and valves 32, 33 for keeping the gas flow amount constant.
A high voltage is applied on the target 27 and the backing plate 28 which become cathodes so as to generate the glow discharge. Particles which are sputtered, scattered from the target 27 are reacted with the O.sub.2 gas from supply 31 so as to be accumulated on the basic plate 25. At this time when Te is used as the target 27, the reaction of Te with O.sub.2 is caused by plasma on the surfaces of the target 27 so as to form Te oxide on the surfaces of the target 27. The O/Te ratio of the Te oxide thin membrane is determined by the ratio of the oxide forming speed and the sputtering speed of the target 27. The O.sub.2 gas partial pressure, i.e., O.sub.2 gas amount which is correlated to the oxide forming speed is varied, so that the O/Te ratio of the Te oxide membrane may be varied.